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Derivative Instruments - Cash flow hedges (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | $ (237,000) | $ 1,957,000 | $ (799,000)
Parent Company [Member] |  |  |
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | (237,000) | 1,957,000 | (799,000)
Cash Flow Hedging |  |  |
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | 533,000 | 1,061,000 | 69,000
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) | 359,000 | (621,000) | (25,000)
Significant ineffectiveness on held hedges | 0 |  |
Cash Flow Hedging | Interest rate contract | Interest expense [Member] |  |  |
Effects of derivative instruments |  |  |
Amount of Gain Recognized in OCI on Derivatives (Effective Portion) | 533,000 | 1,061,000 | 69,000
Amount of Gain (Loss) Reclassified from Accumulated OCI into Income (Effective Portion) | $ 359,000 | $ (621,000) | $ (25,000)

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